Patent GB-992004-A (GB)
Title: Improvements in compressor units
IPC: F04C18/16
Filed: 1961-05-26
Abstract: 992,004. Compressors; screw compressors. ATLAS COPCO A.B. May 26, 1961 [June 2, 1960], No. 19056/61. Headings F1C and F1N. In an air compressor unit, a compressor has a low pressure portion 2 and a high pressure portion 3 into which cooling liquid, e.g. oil, is injected through nozzles 47, 48, air being led to the compressor through an air intake pipe 1 and a control valve casing 6, in which is disposed a pneumatically balanced spring-loaded twin throttle valve 7, 8, and being delivered through a conduit 12, a cyclone type oil separator 14 and a disc type oil separator 17 to a receiver chamber 22, the control valve 7, 8 being movable from a first seated position in which it restricts air flow to the compressor to a second position in which the flow is not restricted, in response to the pressure of the cooling oil, and being movable from the second position to the first position in response to the air delivery pressure. The compressor is preferably of the screw type but may be a sliding vane rotary compressor or a reciprocating piston compressor. Oil collected in the separator 17 and the chamber 22 is delivered by a gear pump 35 to a collecting tank 15 of the separator 14, the oil being drawn from the tank 15 by a gear pump 37 and pumped through a conduit 39, an oil cooler 40, a filter 45 and a check valve 49 to the injection nozzles 47, 48. The pump 37 and cooler 40 have spring-loaded by-pass valves 52 and 43, respectively, valve 52 being adjustable, and the check valve 49 comprises a valve member 50 which is loaded by a weak spring and by the difference in pressure between that of the oil being injected into the compressor and that of the oil in the tank 15. The control valve 7, 8 is connected to a piston 66 movable within a casing 67 to which oil from the pump 37 is led by way of a conduit 72; the valve is also connected to a piston 53 of a compressor unloading device to which compressed air is led from the receiver chamber 22 by way of a conduit 56, the air passing through a conduit 57 in the device to the control valve casing 6 under the control of a needle valve 59 and the piston 53. The receiver chamber 22 is also connected to the unloading device by way of a conduit 61, a control valve 62 and a conduit 63, the valve 62 having a vent passage 64 therein. The valve casing 67 also houses a spring loaded piston 68 connected to a manually operable button 71 and controlling the oil supply to the casing. When the compressor is started the valve 7, 8 is seated and the compressor runs idle. To load the compressor button 71 is pulled allowing oil pressure to open the valve 7, 8 which remains open until a predetermined air-pressure is reached whereupon the valve 62 opens allowing air pressure to close the valve 7, 8 during which time a small quantity of air passes from the receiver chamber 22 through the conduit 56 and the unloading device to the compressor intake. Upon the air pressure being reduced the valve 62 closes and allows the air in the conduit 63 to be vented to atmosphere, thus allowing oil pressure to again open the valve 7, 8. The air delivery conduit 12 is provided with a spring- loaded check valve 13 and air is delivered from the receiver chamber 22, through a spring- loaded check valve 75. Specifications 992,005 and 992,006 are referred to.